Process of and apparatus for distilling glycerine



Nov. 1, 1932. o. H. WURSTER 1,885,156

PROCESS OF AND APPARATUS FOR DISTILLING GLYCERINE Filed F'eb.,13, 1928 4 Sheets-Sheet 1 Nov. 1, 1932. o. H. WURSTER 1,385,166

PROCESS OF AND APPARATUS FOR DISTILLING GLYCERINE Filed Feb. 13, 1928 4 Sheets-Sheet 2 Nov. 11, 1932. o. H. WURSTER 1,385,166

PROCESS OF AND APPARATUS FOR DISTILLING GLYCERINE Filed Feb. 13, 1928 4 Sheets-Sheet s Nov. 1, 1932. o. H. WURSTER 1,885,166

PROCESS OF AND APPARATUS FOR DISTILLING GLYCERINE Filed Feb. 15, 1928 4Sheets-Sheet 4 i I a w :1 Al g x /q dag 4g Patented Nov. 1, 1932 UNITED STATES PATENT OFFICE OSCAR H. WUBSTER, OI CHICAGO, ILLINOIS PROCESS 01' AND APPARATUS FOR DISTILLING GLYCEBINE Application fled February 13, 1928. Serial No. 253,827.

My invention relates to various new and glycerine, and the superheated steam was then useful improvements in distilling processes injected into the glycerine in the still, to aid and apparatus for distilling glycerine and in the distillation thereof. This was a desirrelates to a process and apparatus similar able improvement insofar as the conservation 5 to that disclosed in my co-pending applicaof heat was concerned. The steam for distill- 53 tion Serial No. 253,826, filed on even date ing was generated under vacuum and at relaherewith. Glycerine is a liquidwhich shows tively low temperature, and could thus be a tendency to partially decompose when disgenerated by means of the exhaust heat from tilled directly or alone at normal atmospheric other parts of the process such as the still,

pressure. It is, therefore, distilled in a parthe concentrator, and the pumps. The low s tial vacuum, whereby the boiling point of the temperature steam was superheated by vapors liquid is lowered in accordance with the defrom the distilling glycerine, thus absorbing gree of exhaustion. A gas or vapor, such as, heat while at the same time cooling and parfor example, steam, may be injected into the tially condensing these vapors.

" glycerine to be distilled so that a condition is In the operation of these older processes, brought about in which the sum of the vapor 5 I found the following objections and shortpressures of the glycerine and that of the vacomings coupled with their specific advanpors, or gas, which is introduced to facilitate tages. The process whichvused steam from the distillation is greater at a given temperathe boiler, expanding and superheating the ture than the vapor pressure of the glycerine steam to be injected, while giving expanded and in this manner the boiling point is lowand superheated steam of high temperature, ered, enabling the distillation process to be had a high steam consumption, and was carried out at a lower temperature and withtherefore costly in operation. The high out harmful effect upon the glycerine. The temperature, however, resulted in a high two methods referred to above, namely, cartotal recovery of product from the still resrying out the distillation under partial vacidue. The process which evaporated by uum and introducing a vapor to increase the means of waste heat the previously condensed vapor pressure and lower the boiling point dlute liquors and superheated theresulting of the mixture may be combined for the pursteam by the vapors arising from the dispose of preventingapartial decomposition of tilling glycerine, was economical in steam the glycerine and to otherwise improve the consumptlon but did not give still temperaprocesses of distillation as will be described tures hi h enough to be conducive to a high lat r. yield of glycerine from the crude liquid.

In the distillation of glycerine it is desir- That this would be so can be clearly under- 35 able to use superheated steam as the fluid to stood on a consideration of the conditions. 55 be injected into the glycerine. It is desirable The steam to be injected being heated by the to superheat the steam prior to its injection, vapors from the distilling glycerine, said since the temperature of saturated steam at superheated steam would not, in practice, in the vacuum existing in the still is below the passing through the superheater reach the temperature of distillation of the glycerine. temperature of the distilled vapors. Fur- In some former processes of distillation, thermore, the vapors arising from the dissteam from a boiler was expanded and supertilling glycerine are in practice at a lower heated in a special vessel and this steam was temperature than the impure glycerine then injected into the glycerine. This procliquid itself. Therefore, the injected superess was improved by generating steam under heated steam in this older process has the vacuum from the dilute liquor obtained from actual effect of cooling the glycerine liquid the condensation of the steam used in a prein the still. The heat required for distillavious distillation. This steam so generated tion must therefore be made up from the under vacuum was then superheated in aheat heat transmitted from the high pressure exchanger by the vapors of the distilling steam in the closed coil in the still. There is 1 therefore a retardin effect on the process of distillation which iecomes more and more pronounced as the process proceeds and the residue accumulating in the still becomes heavier and thicker. High still temperatures are desired at the finish of a run to effect a high recovery of the glycerine from the still residue or foots. But as the end of a run is approached the amount of glycerine vapors passing over with the steam becomes less and less. Therefore, the steam to be injected has in the older process less heat transferred to itself and goes to the still at a lower temperature. As the I'GSYdllB in the still becomes thick and heavy the heat from the still coils is conducted through the mass less readily and less effectively. The results of these conditions are that the capac1ty of the apparatus is reduced and it becomes 1mpossible to remove and recover as much of the glycerine, from the residue or foots, as can be recovered at higher still temperatures.

. Such glycerine is then lost in the residue or foots, or must be recovered so far as practical in some subsequent recovery process, adding to the cost and trouble of the operation. I I found that it would be desirable and would improve the process of d*st1llat1 on and increase the yield if the expanded 1njected steam would be brought to a temperature above the temperature of the vapors 1n the still and equal to or highenthan the temperature of the liquid in the still, so that the injected steam would impart heat to the process of distillation instead of absorb heat as in the former process last described.

It is the object of my invention to economize heat in my process and at the same time to bring the temperature of the steam which is to. be injected into the still to a temperature equal to or above the temperature of the liquid in the still prior to its 1n ect1 on.

Another object of my invention conslsts in the installation of a high temperature superheater in the steam line between the still and the heat exchanger in which the steam from the evaporator or from the concentrator ispreheated by the vapors arising from the liquid in the still.

Another object of the invention is to superheat the partially superheated steam in the superheater to a temperature equal to or above the temperature of the liquid in the still.

Another object is to improve the quality of the distilled glycerine by removing more effectively the impurities of the crude glycerine.

Another object is to increase the yield of pure distilled glycerine by a more complete recovery of the glycerine, accomplished by leaving less glycerine in the foots or still residue, and by producing a larger percentage of finished pure glycerine in one operation, thus eliminating losses due to re-handling.

Another object is to accomplish the abovementioned results efliciently and economically with a low steam consumption.

My invention is exemplified in the combination and arrangement of parts shown in the accompanying drawings and described in the following specification and in the steps of the process disclosed therein.

The numbers on each drawing refer to the same or to corresponding parts of the equipment.

In the drawings- Fig. 1 shows one general arrangement in elevation of a complete distilling unit to which my invention applies;

liig. 2 shows one plan of such a distilling uni Fig. 3 is a diagrammatic elevation of the still, catchall, preheater, receiver, evaporator, superheater and connectin piping with parts 1n section showing one orm of apparatus comprised in the present invention and suitable for carrying out the process as described;

Fig. 4 is an elevation of the centrifugal se arator, with parts broken away; and

ig. 5 is a section on the line 55 of Fig. 4.

As shown in the drawings, the numeral designates a still. This still is provided with a heating coil 11 with steam line 12 controlled by valve 13 leading to the coil and steam line 14 leading away from the still heating coil. The still is further provided with expanded and superheated steam inlet pipe 15 leading to open spider 16v from which the steam is injected into the glycerine to be distilled. The still is of such depth that bafiles 17 may be placed in the top to stop entrained particles.

The mixed vapors arising from the liquid pass out of the still through pipe 18 through centrifugal separator 19. Entrainment separated in this centrifugal separator returns to the still through pipe 20. The hot still vapors pass from the centrifugal separator through pipe 21 to the preheater-condenser 22. In the preheater-condenser the mixed vapors are partially cooled and some of the glycerine is condensed. The remaining vapors and condensed liquid pass through pipe 23 to preheater-receiver 24 where the liquid is separated from the vapors. The vapors pass through pipe 25 to cooler-condenser 26. Here most of the remaining glycerine is condensed from the mixed vapors and passes through pipe 27 to cooler-receiver 28 where the condensed glycerine liquid is separated from the remaining water and glycerine vapors. The condensed glycerine from the preheater-receiver 24 and the cooler-receiver 28 passes through pipes 29. 30 and 31 back to the still 10 or through pipe 32 to the concentrator 41, as desired. Suitable control valves 33 and 34 are provided for this purpose. By-pass l ne with control valve 36 is provided so that the glycerine may be diverted to the sweet-water evaporator for reasons explained below.

The water vapor containing a small amount of glycerine vapor and non-condensable gases from cooler-receiver 28 pass through pipe 37 to the sweet-water condenser 38. Here the water vapor and remaining glycerineare condensed and passing through pipe 39 to sweet'water receiver 40 flow through pipe 42 to sweet-Water evaporator 43. The separated non-condensable gases pass through pipe 44 to vacuum pump 45.

The vacuum pump is of a type which will pull a vacuum on the system of between 29" and 30" referred to a 30" barometer. It is one of the features of my invention that my process is operated at a vacuum of above 29" referred to a 30" barometer. Glycerine distilling equipment has heretofore been operated at 26" to 29", but I have found that better quality of glycerine and higher yields are obtained at a vacuum above 29". As previously stated, all figures refer to a 30" baof my invention.

The sweet-Water evaporator 43 may be heated by steam from any suitable source, but as shown the exhaust steam from the high pressure coil in the concentrator 41 passes through pipe 46 tothe steam inlet of the sweet-water evaporator and the exhaust steam from the high pressure steam chamber of the superheater 47 passes through pipe 48 to the steam inlet of the sweet-water evaporator. Suitable control valves 49 and 50 are provided on these lines as shown.

'The vapor from the vapor chamber of the first-efiect evaporator 43 passes through the vapor pipe 51 to the calandria of the secondeffect evaporator 52. The condensation from the calandria of the second-effect evaporator is removed through pipe 53 and condensation pump 54. This eliminates the volatile impurities from the system.

The second-effect evaporator contains pure water. The steam or vapor passes off from the second-effect evaporator under a vacuum of 24 to 26 corresponding to temperature of approximately 140 to 125 Fahrenheit, through pipe 55 to the preheater-condenser 22, which is a special form of counter-current heat exchanger. Here the vapor or steam from the evaporator is superheated to a temperature somewhat below the temperature of the vapors-coming from the still. This is so because the superheating is done by the vapors arising from the glycerine liquid in the still. The temperature to which the steam is superheated in the preheater-condenser has keen observed to be from 285 to 300 Fahreneit.

The partially superheated steam from the preheater-condenser 22 passes through pipe 56 to superheater 47. This superheater may be heated by any suitable means such as by being oil or gas fired or steam heated. 'A means of heating which is readily controlled is naturally to be desired. I have found as an especially desirable form of superheater one in which the partially superheated steam is heated to its desired temperature by high pressure steam from the same source as the steam which is used in the closed coil of the still for heating the still. I have also found as desirable the method of connecting this final superheater in such a way that the heating steam from the outlet of the still heating coil passes next through the superheater. The heating steam outlet of the superheater can then be connected to the heating steam inlet of the evaporator, thus effecting an eflicient use of the available heat. As shown at 47, the superheater is heated by high pressure steam from the outlet pipe 14 of the still heating coil 11. With steam at 200 pounds gauge pressure the superheater may thus be heated to a temperature of approximately 387 Fahrenheit and the steam which has already been superheated to about 285 to 300 Fahrenheit in the preheater-condenser is further superheated to a temperature above the temperature of the vapors rising from the still and to a temperature equal to or higher than the temperature of the liquid in the still. The. temperature of the superheated steam may be raised in the superheater to-a temperature of from 350 to 375 Fahrenheit using heating steam at 200 pounds pressure and to higher temperatures with heating steam at higher pressures or with the heating steam superheated.

The superheated injection steam, prepared as described above, next passes through pipe 57 into the still pipe 15 and into the open steam distributing spider 16 in thebottom of still 10. The expanded and superheated steam is here injected into the body of the liquid, which is under a vacuum of approxi:

mately 29" and facilitates the distillation thereof.

By preheating and further superheating the expanded injection steam as described above, my invention brings-about a continis made in properly constructed and clean equipment are volatile impurities carried over in the vapor state, liquid impurities and dissolved solids. The volatile impurities can to a large extent be made to pass on to the sweet-water by the control of the condenser temperatures of my process and equipment. The liquid and dissolved solid impurities are carrier out of the still by entrainment with the glycerine and water vapors. The usual construction of stills has been to make them of large diameter and shallow. In some cases the diameter and height have been equal and in other cases the height has somewhat exceeded the diameter. I make the height over twice the diameter so that there is room in the top of the still for bafiles to hold back the larger entrained particles. To separate from the glycerine vapors the very small entrained particles of impurities, I place in the vapor line next to the still an effective centrifugal entrainment separator which returns the entrainment to the still and allows only pure vapor to pass on to the condensers.

It will be seen that I economize heat in my novel process and at the same time bring the temperature of the injected steam to a temperature equal to or above the temperature of the liquid in the still prior to its injection. By this means I not only effect all of the economies inherent in using waste heat from various .sources for generating the steam under vacuum and of transferring heat from the vapors of the distilling glycerine to the steam to be injected and by this means partially cooling and condensing said vapors from the distilling glycerine, but I also increase and maintain the rate of distillation in my apparatus because of this increase of temperature of my injected superheated steam and I thus make it possible to have a high temperature in the still at and near the end of the run, thus accomplishing the greatly desired result of a higher recovery of glycerine from the still residue or foots. With suit-ably high temperature and high vacuum this final recovery of the liquid glycerine from the foots may be carried to such 'tion steam in the still.

a degree of completion that the residue or foots may be discarded as practically useless, and thus eliminate the cost and trouble of any further recovery process.

. Reference has heretofore been made to the steam economies effected by concentrating the dilute liquors condensed in a previous distillation by means of the waste heat from other parts of the equipment and using the steam so generated under vacuum for injec- The liquor concentrated in the evaporator and supplying the injection steam isthe sweet-water condensed in the final condenser. In addition to containing 1% to 2% of glycerine this sweet water also contains in solution the volatile impuritiespassing off from the still and not condensed at the high temperature at which I operate my two glycerine condensers, known as the preheater-condenser and the cooler condenser.

Obviously, on boiling this sweet-water in the evaporator under vacuum these volatile impurities again pass off. If the vapors from the evaporator be injected into the still, these volatile impurities of the crude glycerine will be reintroduced into the system.

To overcome this objection and at the same time retain the advantage of using waste heat from other parts of the process, I use in my process the double-effect evaporator. The impure sweet-water is evaporated in the first-effect by means of exhaust steam from the concentrator and superheater and under vacuum of approximately 12" to 14". The vapors from the first-effect pass to the calandria of the second-effect where they are con densed together with the volatile impurities which pass off with the vapors from the boiling sweet-water in the first-effect. This condensate is removed from the calandria of the second-effect by a pump, as is customary in double effect evaporation, and the volatile impurities originally in the crude glycerine are thus permanently removed from the system. In the second-effect evaporator pure water is boiled under a vacuum of about 24 to 26". Thus the vapors generated from pure water only are injected into the glycerine in the still. This, therefore, is one of the features of my improvement which results in the production of pure glycerine in i one operation at low steam consumption.

The evaporators which I use in my process are designed in accordance with Patent N 0.

1,508,180, issued to Walter E. Sanger, September 9, 1924. The use of evaporators of this design results in further steam economy.

Since my process and apparatus produces pure glycerine in one operation, provision is desired to permit returning to the still or to some othervessels impure fractions obtained in any part of the cycle so as to keep the pure fraction separate. At the commencement of operation andagain when running down to foots fractions are obtained which are impure. Provision is therefore made that such fractions of glycerine can be returned direct to the still or the sweet-water evaporator by a simple arrangement of-piping and valves.

A vapor conduit conducts the vapors from the concentrator 41 back to the sweetwater condenser 38.

I have found a centrifugal separator of the type shown in detail in Figs. 4 and 5 to be very efficient in carrying out my process. This separator is claimed in the co-pending application, Serial No. 114,627, filed June 9, 1926, by Daniel M. Flick, and includes a spiral plate 66 which gives the vapors entering the pipe 18 a whirling motion as they pass down to the mouth The longitudinal plates 61 and- 62, together with the flan es 63 on the plates 61, form a series of dea air spaces between the plates and the shell 19 of the separator. A small space is left between the overlapping plates through which the condensed partlcles pass into the dead air space. The condensed mo1sture then runs down through the perforated plate 64 back to the still. It is a feature of my inventlon that by .the process and equipment as described I can produce pure glycerine almost as soon asthe equipment is heated up and distillatlon starts. This time has been found to be from slightly less than thirty minutes to about forty-five minutes. This feature is here pointed out because by older processes several hours are required before the highest quality of distilled glycerine is producedand therefore very large portions of the distilled glycerine must be redistilled. This entails additional distilling costs and addltlonal losses due'to rehandling, all of which objections are obviated by my improvements.

It should be noted that my invention is not limited strictly to the various details of the process and of the apparatus whichhave been particularly described, but that the same is as broad as is indicated by the accompanying claims.

I claim 1. In an apparatus for distilling glycer ne, a still, a glycerine condensenwlth receiving means therefor and a sweet-water condenser with receiving means therefor connected with said still, evaporators having the vapor chamber of one connected to the calandria of another, a conduit connecting said sweet-water receiver with the vapor chamber of said firstmentioned evaporator, a conduit connecting the vapor chamber of said last-mentioned evaporator with said still, said last-mentioned evaporator constituting the source of distilling steam for the liquid in said still, a concentrator connected with said glycerine condenser, a steam connection into the heating coil of said concentrator for heating the same, and a steam connection from the heating coil of said concentrator to the calandria of said first-mentioned evaporatorv through which the exhaust steam from flows. v

2. In an apparatus for distilling glycerine, evaporators having the vapor chamber of one connected with the calandria of another, a still, a glycerine receiver, means for mainsaid concentrator taining said still at distilling temperature, a

preheating condenser having a conduit connecting said still with the vapor chamber of said last-mentioned evaporator, and a conduit connecting said still with said glycerine receiver through said preheating condenser to of the exit pipe 21.

preheat the vapor from said evaporator by the vapor from said still, a sweet-water condenser having a receiver connected with the vapor chamber of said first-mentioned eva orator, a superheater between said preheating condenser and stillin the condult connecting said evaporator and still, and means for heat-thevapor from said evaporator by the vapor from said still, a sweet-water condenser having a receiver connected with the vapor chamber of said first-mentioned evaporator, a superheater between said preheating condenser and still in the conduit connecting said evaporator and still, and a concentrator having a liquid connection to said glycerine receiver and a vapor connection to said sweetwater condenser.

4. In an apparatus for distilling glycerine, evaporators having the vapor chamber of one connected with the calandria of another, a still, a glycerine receiver, a steam coil .for maintaining said still at distilling temperature, a preheating condenser having a conduit connecting said still with the vapor chamber of said last-mentioned evaporator and a conduit connecting said still with said glycerine receiver through said preheating condenser to preheat the vapor from said evaporator by the vapor from said still, a sweet-water condenser having a receiver connected with the vapor chamber of said first-mentioned evaporator, a superheater between said preheating condenser and still in the conduit connecting said evaporator and still, and a vacuum pump formaintaining said apparatus under high vacuum. said steam coil having a connection with said superheater through which steam passes to heat said superheater.

5. In an apparatus for distilling glycerine, evaporators having the vapor chamber of one connected with the calandria 'of another, a

still, a glycerine receiver, means for maintaining said still at distilling temperature. a

preheating condenser having a conduit connecting said stlll" with the vapor chamber of said last-mentioned evaporator and a conduit 3 connecting said still with said glycerine receiver through said preheating condenser to preheat the vapor from said evaporator by the vapor from said still,'a sweet-water condenser having a receiver connected with the vapor chamber of said first mentioned eva oglycerine receiver selectively into said still,

rator, a superheater between said preheating concentrator, or evaporator.

In testimony whereof I have si ed my condenser and still in the conduit connecting said evaporator, and still, steam means for heating said superheater, and aconduit connecting the exhaust of said steam means with the calandria of said first mentioned evaporator. I

' mentioned 6. A process of distilling. glycerine under vacuum and in an atmosphere of steam which comprises the injection of superheated steam into the liquid to be distilled, condensing the major part of the glycerine from the mixture of steam and vapor, passing the remaining vapors to a sweet-water condenser where the same are condensed to form a condensate, evaporating the latter condensate andusing the vapors therefrom to evaporate water v under vacuum, preheating the steam formed from said water by the vapors from the distilling li uid, and super-heating the preheatname to this s ecification on this 7t February, A.

ed steam y means of high temperature, steam above the temperature of the vapors arising from the distilling liquid to form the said superheated steam injected into the liquid to be distilled, said sweet-Water being evaporated by the said high temperature steam after being used to superheat the said preheated vapors.

7. In an apparatus for distilling glycerine, a still, a glycerine condenser, condensate receiving means therefor, a sweet-water condenser, sweet-water receiving means for said sweet-water condenser and connected with said still, evaporators having the vapor chamber of one connected to the calandria of another, a conduit connecting said sweet-water receiving means with the vapor chamber of said first-mentioned evaporator, a conduit connecting the vapor chamber of said lastevaporator with said still, said last-mentioned evaporator constituting the source of steam for distilling the liquid in said still, a superheater in said last-mentioned conduit outside of said still, a steam connection into said superheater for heating the same, and a steam connection extending from said superheater to the calandria of said first-mentioned evaporator for carrying exhaust steam to said firstmentioned evaporator to heat the same.

8. In an apparatus for distilling glycerine, a still, a glycerine condenser, a receiver for the condensate from said condenser, a sweetwater condenser, asweet-water receiver for said sweet-water condenser, evaporating *meanshaving a conduit connection with said still, said means constituting a source of distilling steam for said still, a conduit connecting said sweet-water receiver and said evaporating means, a concentrator, a conduit connecting said glycerine receiver with said still, evaporating means and concentrator, and means for directing the liquid in said day of 1928. OSCAR H. WURSTER. 

